On 7/7/21 11:05 PM, Florian Weimer wrote: >> This looks basically like someone dumped a bunch of CPUID bit values and >> exposed them to applications without considering whether applications >> would ever need them. For instance, why would an app ever care about: >> >> PKS – Protection keys for supervisor-mode pages. >> >> And how could glibc ever give applications accurate information about >> whether PKS "is supported by the operating system"? It just plain >> doesn't know, or at least only knows from a really weak ABI like >> /proc/cpuinfo. > glibc is expected to mask these bits for CPU_FEATURE_USABLE because they > have unknown semantics (to glibc). OK, so if I call CPU_FEATURE_USABLE(PKS) on a system *WITH* PKS supported in the operating system, I'll get false from an interface that claims to be: > This macro returns a nonzero value (true) if the processor has the > feature name and the feature is supported by the operating system. The interface just seems buggy by *design*.
